Interesting spot, give me your feedback

+1 to this. Also worth noting that the dynamic of you opening UTG as CL and him 3betting from SB as 2nd in chips is not one that is overly bluffed (same can be said for flop line) I think you may be up against AsAx KsKx or AsKx a lot on this flop. Agree with Ralphy's points, fold flop as played or checking back flop is an option too (but I think I slightly prefer bet/folding flop to eliminate guess work on later streets)

He has all overpairs with spades as well as AKs and the like. Even if he is bluffing here, its a massive losing call long term. Pretty easy fold and move on. What bluffs does he even have here 3betting from SB?

I'd also check behind, but I think we have to call the flop check raise. It is quite small, we have position, and Villain can easily have a naked As here.

Finding bluffs on 4 flush boards is quite hard, and often counter intuitive. All Flush boards are 'the same'.

I don't think the guy second in chips wants to clash with the chip leader - you also open UTG to a full table and he's 3 betting from the SB. He should be extremely strong here - not a spot I would expect someone to be light, and would play it accordingly. Really there's no point in betting this flop - if he's x/f we want to check for him to possibly bluff future streets, him x/r us is a nightmare, and we really don't need protection/deny equity here. Think you punted pretty hard here - now you're on the river with no idea where you're at basically playing for your tournament life.

Agreed, and the 3 bet followed by the check raise feels very much like the above hands. We are giving this player a lot of credit, but wouldn't he just cbet with air? Feels more like he is trapping us into betting, then checking when he hits the nuts, then making a big shove that looks bluffy. It's a neat disguised line.

Given Villain 3-bet from the SB and can easily have a PP > TT with no Spade I would check back the flop. Betting 6.5 bb's won't work anyway if Villain has a spade > T so we are gambling in position and won't know if we are ahead or not if we get called.

Once Villain raises the flop for me its an easy fold. Not just that it was a c/r but the sizing as well. We bet 6.5 bb's and the raise was to 15 bb's. Basically less than 2.5x. So Villain is OOP for the rest of the hand and increasing the pot size by raising an amount that has basically little Fold Equity especially if we have a spade. A normal raise size by villain would be about 20 bb's so that it could be a bluff with FE or a value raise. Why in the world would villain do that without either a flush or A♠A/K♠K ? OK there is one unlikely possibility. Villain could have an overpair like JJ+ with no spade and wants to make a turn jam reasonable if no spade comes. But really I would just call the flop bet and then over jam the turn if that were the case. Also, it would have been smarter to just lead out the flop with 12 bb's and lead jam the turn.

As played, the river is a polarizing shove. But I just don't see a lot of bluffs here. Its a spot that I think would be under bluffed based on the flop c/r. I would just fold. It is likely they got there on the turn and wanted to make it look like they didn't or they were already there on the flop and wanted you to bet with whatever flush you had. Another outside possibility is they could be jamming thinking you didn't have a flush either because you didn't bet the turn and they want to take you away from the chop (a Phil Ivey specialty including the loss when you call with the T♠).